Scotland’s first minister, Nicola Sturgeon. ‘She has responded to the Brexit vote with her accustomed skill, and with a committed pro-European approach that cannot escape favourable comparisons with Jeremy Corbyn’s equivocations or Boris Johnson’s bluster.’
Photograph: Andrew Milligan/PA

The United Kingdom voted to leave the European Union last week. But a very disunited kingdom is now left to pick up the pieces of that dismaying decision. Last week’s vote can be sliced and diced in many ways – age, class, party and education differences among them. Yet the single most destructive dimension of the leave vote was undoubtedly geographical.

It was England outside London, where the overwhelming majority of UK voters live and where turnout was also highest, that took Britain out of the EU last week. Wales, much smaller than England (though currently more successful at football), followed suit more narrowly. Yet voters in three hugely important parts of the UK – Scotland, Northern Ireland and London – now find themselves facing an unwilling exit from a union in which they voted decisively to remain, all with over 55% of the vote. So does Gibraltar, where fully 96% voted to stay.

It must be faced without flinching that these were and are the rules. A simple majority of UK voters sufficed to carry the day, alas. Whether these were good rules is another question but now an academic one. Yet the strain that these rules impose on an already deeply fractured UK – in which national and local feeling is now a much more powerful political reality than it was in 20th century Britain – is palpable, though it was always important in Northern Ireland.

Nowhere is this tension now more politically charged than in Scotland, which re-elected its nationalist government for a third term less than two months ago and where independence has been the central dynamic of electoral behaviour and politics since at least the 2014 referendum on whether to leave the UK. The SNP has always made clear that it would not sit idly by if Scotland was forced out of the EU. Its leader Nicola Sturgeon played a high-profile role in the remain campaign north and south of the border. Now that Scotland is indeed facing removal from the EU against its will, Ms Sturgeon and her party are making it clear that they will fight it all the way. Plenty of anti-independence voters, including the Scottish Labour party, are lending her their support, at least for the moment.

The first minister has responded to the Brexit vote with her accustomed skill, and with a committed pro-European approach that cannot escape favourable comparisons with Jeremy Corbyn’s equivocations or Boris Johnson’s bluster. On Tuesday she told the Holyrood parliament that she was fighting Scotland’s corner on all fronts – in Europe, where she is now heading for talks with EU parliamentarians and, later, the European commission; in London, where she is making sure that David Cameron and his successor are taking Scotland’s interests seriously; and at home, where she has set up a council of experts, some nationalists and some not, to advise on tactics and possibilities. Every weapon at Ms Sturgeon’s disposal is being checked and polished. She deserves widespread support for this ecumenical approach for as long as it lasts, including from pro-Europeans in England.

Last week’s vote raises afresh the question of whether Scotland will remain in the UK. Ms Sturgeon is being canny about that for now, saying a second referendum is highly likely but insisting on Tuesday that it is not in her immediate plans. That claim can be taken with a large pinch of salt; if conditions favour another referendum the SNP would go for it. But Ms Sturgeon knows full well that these are early days and that opinions are divided, not least because of the fall in the oil price. She also knows that to lose a second referendum would be crippling to the SNP.

One of the most outrageous aspects of the leave campaign was its sweeping indifference to the Scottish and Irish consequences of a vote to leave. Ms Sturgeon is right to take a gradualist approach. But no one in any part of the so-called United Kingdom should be in any doubt that last week’s vote has put the very future of the country in doubt.

• This article was amended on 30 June 2016. An earlier version said Scotland, Northern Ireland and London voted decisively to remain, “all with over 60% of the vote”. In Scotland the vote for remain was over 60%, but it was 59.9% in London and 55.8% in Northern Ireland.